Bulldozers and other heavy equipment often operate in a series of repeated motions to accomplish a given task. For example, a bulldozer will cycle through load, carry and spread modes to scrape dirt from a work area and move it to another area. During the load mode the bulldozer scrapes dirt from the work area. During the carry mode, the bulldozer moves the dirt to a second location where the dirt is then distributed in the spread mode. Each of these tasks generally requires that the bulldozer operate at relatively high engine speeds. For short periods of time during these cycles, it may be desirable to decrease the engine speed.
Because the equipment runs at high speeds during most of its operations, it is more convenient to cause the engine to operate at higher speeds without an operator input. Then, during those periods when a slower engine speed is desired, the operator can provide an input that will cause the engine to slow down. After the input is removed, the engine will return to the higher speed.
It is known in the prior art to include a mechanical lever connected to the engine to enable the operator to run the engine at a desired engine speed. In connection with the lever, a deceleration pedal is sometimes provided that permits the operator to reduce the engine speed from that initial speed selected by the lever position. In this manner, the operator can cause the engine to run at the higher engine speeds normally required for the given task. Then, operator input is only required during those brief periods when the engine speed must be slowed.
While such prior art systems make the equipment more convenient to operate, they are cumbersome and expensive to build and maintain because of the numerous mechanical connections and linkages. Such systems also require significant space to make all the necessary mechanical connections and are also difficult to repair. Moreover, it is difficult to detect a malfunction in such systems. Such systems do not provide a default high idle position that can be easily and repeatably selected.
The present invention is directed toward overcoming one or more of the disadvantages of the prior art.